"The decisions on constructing military base settlements on the islands Iturup and Kunashir have been taken and confirmed," the commander of Russia's Far Eastern military district Sergei Surovikov said, Russian agencies reported.
"All the main objects, and there are more than 150 of them, will be completed before 2016," he added.
Troops deployed on the two islands, which Japan considers its territory despite them being claimed by the Soviets in the final days of World War II, will also receive additional equipment, he said.
Relations between Moscow and Tokyo have been strained for decades because of the status of southernmost four of the Pacific islands known as the Southern Kurils in Russia and the Northern Territories in Japan.
One solution mooted in the past could involve Russia ceding control of the two smallest islands of Shikotan and Khabomai and keeping the much larger Kunashir and Iturup.